Method and apparatus for conditioning tobacco



June 4, 1968 w. WOCHNOWSKI 3,386,448

METHOD AND APPARATUS FOR CONDITIONING TOBACCO 7 Filed Sept. 2; 1966 Ila,

L MDEHHK wocmmwsk/ INVENTOR.

Micky; a! ffE/zie, 1143' Arman/g) United States Patent Germany Filed Sept. 2, 1966, Ser. No. 577,015

Claims priority, application Germany, Sept.

20 Claims. ci. 131-135 The present invention relates to a method and apparatus for conditioning tobacco. More particularly, the invention relates to a method and apparatus for expelling surplus moisture from tobacco.

It is already known to regulate the moisture content of tobacco by indirect exchange of heat with steam. A serious drawback of presently known conditioning apparatus which utilize steam is that they react too slowly, i.e., that changes in the rate of steam circulation bring about only gradual changes in the quantity of moisture which is expelled from tobacco. Substantial quantities of tobacco having excessive or insuificient moisture content will be permitted to leave the apparatus before the latter can carry out necessary automatic adjustments in heating action.

Accordingly, it is an important object of the present invention to provide a method of expelling surplus moisture from tobacco in such a way that the moisture content is reduced to a predetermined optimum value even if tobacco which is being treated contains batches of widely different moisture content.

Another object of the invention is to provide a method of effecting controlled expulsion of surplus moisture from a continuous tobacco stream in such a way that fluctuations in the rate at which tobacco is being fed cannot unduly affect the percentage of moisture in conditioned tobacco.

A further object of the invention is to provide a method which can be utilized for controlled expulsion of moisture from Whole or comminuted tobacco leaves.

An additional object of the invention is to provide a conditioning apparatus which can expel surplus moisture from a travelling tobacco stream and can react without undue delay to all, even sudden, changes in moisture content of successive increments in the tobacco stream.

An additional object of the invention is to provide a conditioning apparatus which occupies little room and can process large quantities of tobacco per unit of time.

The method of my invention comprises conveying a stream of moist tobacco leaves, laminae or shreds toward, through and beyond an elongated conditioning zone which may be defined by a rotary cylindrical drier, circulating at least one current of fresh steam in a confining path extending into the conditioning zone so that such steam expels moisture from tobacco and its pressure respectively rises and drops in response to indirect exchange of heat with tobacco having lower and higher moisture content, conveying through the conditioning zone a current of hot gas, preferably concurrent with the tobacco stream, to expel additional moisture from successive increments of the tobacco in the conditioning zone, measuring the pressure of steam in the confining path, and respectively raising and reducing the temperature of hot gas in response to decreasing and increasing steam pressure. The confining path for steam can be defined by one or more sets of piping which extends into the conditioning zone and preferably rotates with the drier to agitate the particles of tobacco.

The hot gas is preferably air and the temperature of such hot gas may be raised or reduced by admixing thereto varying amounts of cooler atmospheric air.

3,386,448 Patented June 4, 1968 In order to further reduce the length of intervals required for adjusting the amount of moisture which is to be expelled from tobacco, the rate of fresh steam flow in the confining path may be varied, either independently of changes in steam pressure or such rate will be respectively increased and reduced in response to decreasing and increasing steam pressure.

In accordance with another feature of the above outlined method, the moisture content of tobacco can be measured downstream of the conditioning zone and the measurement may be utilized to respectively increase and reduce the expulsion of moisture, for example, by changing the rate of fresh steam circulation when the moisture content respectively exceeds and is below a predetermined optimum value.

The method may fiurther comprise the steps of circulating a second current of fresh steam in a second confining path which also extends into the conditioning zone, and regulating the rate of steam circulation in the second path in accordance with the results of the measurement of steam pressure in the first confining path. Otherwise stated, the pressure of steam in the first path will control the rate of admission of steam into the second path but the two bodies of steam need not be maintained at the same pressure.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved conditioning apparatus itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawings, in which:

FIG. 1 is a schematic side elevational view of a tobacco conditioning apparatus which embodies one form of the present invention, a portion of the drier and certain parts of the heating means being shown in vertical section;

FIG. 2 is a diagram illustrating certain components of the conditioning apparatus which is shown in FIG. 1;

FIG. 3 is a similar diagram but showing certain details of a second conditioning apparatus;

FIG. 4 is a diagram showing certain details of a third conditioning apparatus which is similar to the apparatus of FIG. 3; and

FIG. 5 is a diagram showing a modification of the apparatus which is illustrated in FIG. 1.

The conditioning apparatus of FIG. 1 comprises a rotary drier 1 in the form of a cylindrical drum whose axis of rotation is inclined downwardly as seen in the direction in which the tobacco particles advance therethrough. The drier is rotatable on rolls 4 mounted in brackets 2, 3. The drive means for the drier comprises an electric motor 50, a variable-speed transmission 50a driven by the motor 50, a pinion 5 driven by the output shaft of the transmission 50a, and a ring gear 6 provided on the drier and meshing with the pinion 5.

The internal space of the drier 1 constitutes a conditioning chamber or zone 1a which accommodates a heat exchanger composed of steam piping 10 defining a confining path for fresh steam which is fed by a supply pipe 63. The piping 10 rotates with the drier 1 and acts not unlike a set of radially extending vanes or blades to lift tobacco particles from a lower level to a higher level and to then allow such particles to drop by gravity back to the lower level whereby the particles are agitated and each thereof is repeatedly caused to exchange heat with steam. The supply pipe 63 is connected with the nipple 12 of a rotary distributor 13 which admits steam to the piping 10. A discharge pipe 64 conveys spent steam and contains a trap 65 for condensate. Since the drier 1 is inclined and drives the piping, the particles of tobacco admitted by a chute 17 automatically advance through the conditioning zone In and into a chute 52 below the distributor 13. The left-hand end of the drier 1 is open and accommodates the discharge end of a supply conduit 29 which forms part of a heating unit and admits a current of hot air. This conduit is connected with the outlet of a blower 8 whose inlet is connected with a suction conduit 30 accommodating an electric resistance heater 31. The suction conduit 30 further accommodates a regulating valve 9 which can determine the cross-sectional area of an opening 14 for admission of cool atmospheric air. The valve 9 is adjustable by a servo motor 32.

The right-hand end of the drier 1 is closed by a hood 18 having an outlet 21 which is connected with a suction fan 22 serving to evacuate air and vapors from the conditioning zone 1a. The lower portion of the hood 18 is provided with an opening 19 for the chute 52 so that the stream 51 of conditioned tobacco particles can leave the drier. The chute 52 discharges tobacco onto a conveyor belt 40 which delivers such tobacco to a further processing station, not shown. The motor 50 forms part of the conveying system for the stream 51 because it rotates the drier 1 and piping whereby the latter automatically advances tobacco through the conditioning zone 1a.

The supply pipe 63 accommodates a detector constituted by a pressure gauge 60, and a restrictor 61 Which is mounted upstream of the gauge. The restrictor 61 controls a valve 62 which maintains the pressure of infiowing steam at a constant value.

The gauge 60 controls a signal generator 66 which actuates the servomotor 32 for the regulating valve 9.

The heating system of the just described apparatus is shown diagrammatically in FIG. 2 and it will be seen that the temperature of hot air admitted by the supply conduit 29 is a function of steam pressure in the piping 10. The restrictor 61 and valve 62 can be replaced by a conventional throttle valve or constant pressure outlet valve which is capable of maintaining the rate of steam flow at a desired value.

The operation of the apparatus shown in FIG. 1 is as follows:

The motor 50 is started so that the drier 1 begins to rotate. The chute 17 admits a continuous and preferably uniform stream 51 of moist tobacco particles which are entrained and agitated by the piping 10 to advance toward the chute 52. The blower 8 is started to supply hot air into the conduit 29, and the fan 22 withdraws air and vapors from the hood 18. The pipe 63 is connected to a suitable source 200 of steam, and supplies steam into the nipple 12. The circuit of the heater 31 is completed so that the latter heats air which is being sucked from the atmosphere via conduit 30. It is clear that the heater 31 may be replaced by a steam heater or by another suitable heating device which can raise the temperature of inflowing air. If a certain part of the tobacco stream admitted by the chute 17 has a higher than average moisture content, the pressure of steam in the pipes 10 drops because the condensation of steam progresses more rapidly. The gauge 60 senses such drop in steam pressure and transmits an impulse to the signal generator 66 which operates the servomotor 32 in a sense to reduce the opening 14 and to thus raise the temperature of hot air in the conduit 29. The valve 9 then admits a lesser quantity of cool atmospheric air so that the major part of air admitted by the conduit 29 exchanges heat with the electric heater 31. The current of hot air entering the condition.- ing zone 1a expels more moisture and the moisture content of successive increments entering the chute 52 does not exceed a desirable optimum value.

If the chute 17 admits tobacco with lower than normal moisture content, the gauge 60 senses a rise in steam pressure and the valve 9 is adjusted by servomotor 32 to admit more atmospheric air. The temperature of hot air issuing from the pipe 29 drops and such air then expels less moisture.

The current of hot air which issues from the supply conduit 29 will bring about rapid changes in moisture content of tobacco which travels through the zone 10. Thus, the currents of steam which circulate in the piping 10 will expel a certain minimum amount of moisture from tobacco in the drier 1, and the heating unit including the parts 8, 9 and 2931 will expel additional moisture above such minimum amount. Since the current of hot air comes in direct contact with tobacco, changes in its temperature will bring about immediate changes in moisture content so that the increments leaving the drier via chute 52 will contain a desired amount of moisture. The rate of steam admission into the piping 10 can be changed from time to time, for example, if the person in charge notes that the rate of fresh air admission through the opening 14 consistently exceeds an average rate. This can be determined by direct observation of the position of the valve 9 or by observing the gauge 60 which is preferably provided with a calibrated scale. The conditioning effect of the current of hot air can be selected in such a way that it is felt along the full length of the zone 111. However, the effect of hot air will be felt mainly in the upstream section of the conditioning zone. The accuracy of the conditioning action depends on the sensitivity of the gauge 60 and on the inertia of the operative connection between the gauge and the regulating valve 9.

The exact construction of the signal generator 66 and servomotor 32 forms no part of the present invention. Such devices are well known in the art and are available on the market.

In the embodiment which is shown diagrammatically in FIG. 3, the drier (not shown) rotates two sets of piping 71 and 72. These sets replace the piping 10 and are respectively installed in the downstream and upstream sections of the conditioning zone. The direction in which the tobacco stream advances through the conditioning zone is indicated by arrow 73. A detector or pressure gauge is installed in the supply pipe 81 which delivers steam to piping 72. The numerals 90 and 91 denote two condensate traps which are respectively installed in discharge pipes 81a, a for conveying spent steam from the piping 72, 71. The gauge 80 controls a signal generator 82 having two outputs one of which is connected with the servomotor 83 for a regulating valve 84 corresponding to the valve 9 of FIG. 1. The other output of the signal generator 82 is connected with a second regulating valve 86 installed in a supply pipe 85 which admits fresh steam into the piping 71. The valve 86 admits more steam when the gauge 80 detects a drop in steam pressure in the piping 72 and reduces the flow of steam into the piping 71 when the steam pressure in the piping 72 rises. In this way, the pressure of steam in the piping 72 controls the temperature of hot air which is admitted into the upstream section of the conditioning zone concurrent with the tobacco stream, and the heating action of steam in the downstream section of the conditioning zone.

If the moisture content of tobacco entering the conditioning zone is too high, the amount of heat energy must be increased. This is indicated by a drop in steam pressure in the piping 72 whereby the gauge 80 causes the signal generator 82 to effect an adjustment of the regulating valves 84, 86 in a sense to raise the temperature of infiowing air and to admit more steam into the piping 71. The current of hot air exchanges heat with tobacco in the upstream section of the conditioning zone and the steam circulating in piping 71 exchanges heat with tobacco in the downstream section of the conditioning zone. Inversely, and if the moisture content of tobacco in the drier is below an average value, the valve 84 admits more atmospheric air and the valve 86 reduces the rate of fresh steam admission into the piping 71.

It will be noted that the steam pressure in piping 72 is independent of the steam pressure in piping 71. The supply pipes 81, 85 can receive steam from a common source 200. Due to the fact that the gauge 80 is installed in the supply pipe 81 for the upstream piping 72, the valve 84 can be adjusted with a minimum of delay, i.e., shortly after a. mass of tobacco particles having a higher or lower than normal moisture content enters the upstream section of the conditioning zone. Thus, the inertia of the heating system is low which is desirable because the moisture content of tobacco leaving the drier will approach more closely a desirable optimum value.

Adjustment of the regulating valve 86 in response to signals transmitted by the device 82 will bring about a gradual change in the heating action of the piping 71. However, this is of no detriment because the device 82 simultaneously adjusts the regulating valve 84 which changes the temperature of infiowing air without appreciable delay so that the apparatus can immediately expel a higher or lower percentage of moisture, depending on the steam pressure detected by the gauge 89.

Since the gauge 80 is installed in the pipe 81 and the regulating valve 86 is installed in the pipe 85, changes in steam pressure brought about by adjustment of the valve 86 will not affect the adjustment of valve 84. Thus, the rate of steam admission into the piping 72 is not infiuenced by the rate of steam admission into the piping 71.

Referring to FIG. 4, there is shown an apparatus which is similar to the apparatus of FIG. 3 and certain components of which are identified by similar numerals each preceded by the digit 1. The regulating valve 86 of FIG. 3 is omitted but the apparatus of FIG. 4 comprises a second detector 94 which measures the moisture content of successive increments of tobacco on the conveyor belt 40 (see also FIG. 1). This detecor controls a signal generator 93 which can adjust a regulating valve 92 in the pipe 181 supplying fresh steam to the upstream piping 172.

When the moisture content of tobacco in the stream which has left the conditioning zone is higher than desired, the detector 94 causes the signal generator 93 to adjust the valve 92 so that the piping 172 receives more steam. If the moisture content of conditioned tobacco is too low, the detector 94 causes the signal generator 93 to adjust the valve 92 in a sense to reduce the rate of fresh steam flow into the piping 172.

The manner in which the gauge 180 controls the regulating valve 184 is the same as described in connection with the valve 84 of FIG. 3. A moisture detector which can be used in the apparatus of FIG. 4 is disclosed, for example, in the copending application Serial No. 411,788 of Hans Koch et al. which is assigned to the same assignee.

The apparatus of FIG. 5 is similar to the apparatus of FIG. 2 and its components are denoted in part by similar reference numerals each preceded by the digit 1. The restrictor 61 is replaced by a regulating valve 95 which is installed in the supply pipe 163 for the steam piping 110. The signal generator 166 has two outputs one of which controls the servomotor 132 for the regulating valve 109 and the other of which controls the valve 95.

When the gauge 160 detects a substantial drop in steam pressure, the signal generator 166 causes the regulating valve 95 to admit more steam into the piping 110. This results in more rapid change in heating action so that the exchange of heat between tobacco and steam is intensified simultaneously with intensified heat exchange between tobacco and the current of hot air. The valve 95 will reduce the inflow of steam if the gauge 160 detects a rise in steam pressure.

Without further analysis, the foreging will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of my contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is:

1. Apparatus for conditioning tobacco, comprising a drier defining a conditioning zone; conveyor means for advancing moist tobacco through said zone; heat exchanger means including steam piping extending into said zone and a source of steam connected with said piping for admitting thereto fresh steam whereby such steam expels moisture and its pressure in said piping repectively drops and rises in response to indirect exchange of heat with tobacco whose moisture content respectively exceeds and is below a normal value; detector means for measuring the steam pressure in said piping; and a heating unit comprising conduit means for admitting into said zone a hot gas which expels moisture by direct exchange of heat with tobacco in said drier, said heating unit further comprising regulating means operatively connected with said detector means for varying the temperature of hot gas as a function of steam pressure in said piping so that the gas temperature respectively rises and drops in response to decreasing and increasing steam pressure.

2. Apparatus as set forth in claim 1, wherein said gas is air and wherein said heating unit comprises an air heater and means for conveying heated air from said heater to said conduit means, said regulating means comprising an adjustable valve arranged to admit varying amounts of atmospheric air into the air which has been heated by said heater.

3. Apparatus as set forth in claim 1, further comprising second regulating means provided between said source and said piping and operatively connected with said detector means to respectively reduce and increase the rate of steam admission in response to increasing and decreasing steam pressure in said piping.

4. Apparatus as set forth in claim 1, further comprising second heat exchanger means including second steam piping extending into said zone and connected with said source to receive steam independently of said first mentioned piping and to bring about expulsion of additional moisture by indirect exchange of heat between steam in said second piping and tobacco in said zone.

5. Apparatus as set forth in claim 4, wherein said conditioning zone comprises an upstream section and a downstream section and wherein moist tobacco enters said downstream section after passing through said upstream section, said first mentioned and second pipings being respectively installed in the upstream and downstream sections of said zone.

6. Apparatus as set forth in claim 5, further comprising second regulating means provided between said source and said second piping and operatively connected with said detector means to respectively reduce and increase the rate of steam admission into said second piping in response to increasing and decreasing steam pressure in said first mentioned piping.

7. Apparatus as set forth in claim 1, further comprising second detector means for measuring the moisture content of tobacco which issues from said conditioning zone, and second regulating means provided between said piping and said source and operatively connected with said second detector means to respectively increase and reduce the rate of steam admission to said piping when the moisture content determined by said second detector means respectively exceeds and is below a predetermined value.

8. Apparatus as set forth in claim 1, further com-.

prising second detector means for measuring the moisture content of tobacco which issues from said conditioning zone, and second regulating means for respectively effecting expulsion of greater and lesser quantities of moisture in said zone when the moisture content determined by said second detector means respectively exceeds and is below a predetermined value.

9. Apparatus as set forth in claim 1, wherein said drier is a cylinder rotatable about an axis which is slightly inclined with reference to a horizontal plane and wherein said piping is rotatable with said cylinder to agitate tobacco in said zone.

10. Apparatus as set forth in claim 9, wherein said conveyor means includes means for rotating said cylinder.

11. Apparatus as set forth in claim 9, wherein said conduit means is arranged to admit hot air concurrent with the travel of tobacco through said conditioning zone and wherein said regulating means comprises adjustable valve means for admitting atmospheric air into said conduit means.

12. Apparatus as set forth in claim 1, further comprising means for regulating the flow of steam from said source to said piping.

13. A method of expelling moisture from tobacco, comprising the steps of conveying moist tobacco through a conditioning zone; circulating at least one current of fresh stream in a confining path extending into said zone whereby such steam expels moisture from tobacco and its pressure respectively rises and drops in response to indirect exchange of heat with tobacco of lower and higher moisture content; conveying through said zone a current of hot gas in direct heat exchanging relationship with tobacco to expel therefrom additional moisture; measuring the pressure of steam in said confiining path; and respectively raising and reducing the temperature of hot gas in response to decreasing and increasing steam pressure.

14. A method as set forth in claim 13, wherein said last mentioned step comprises mixing said hot gas with varying amounts of a cooler gas.

15. A method as set forth in claim 13, further comprising the step of respectively increasing and reducing the rate of fresh steam flow in said path in response to decreasing and increasing steam pressure.

16. A method as set forth in claim 13, further comprising the step of varying the rate of fresh steam circulation in said confiing path.

17. A method as set forth in claim 13, further comprising the steps of measuring the moisture content of tobacco downstream of said conditioning zone, and respectively increasing and reducing the rate of fresh steam flow in said confining path when the moisture content of tobacco downstream of said zone respectively exceeds and is below a predetermined value.

18. A method as set forth in claim 13, further comprising the step of circulating a second current of fresh steam in a second confining path also extending into said conditioning zone whereby the second current eXpels additional moisture in response to indirect exchange of heat with tobacco, and respectively increasing and reducing the rate of fresh steam flow in said second confining path in response to decreasing and increasing steam pressure in said fist mentined path.

19. A method as set forth in claim 13, wherein said hot gas is admitted concurrent with the direction of tobacco travel through said conditioning zone.

20. A method as set forth in claim 19, wherein the tobacco is conveyed through said conditioning zone in the form of a continuous stream, and further comprising the step of agitating tobacco in said zone.

References Cited UNITED STATES PATENTS 473,263 4/1892 Proctor 131-136 X 1,393,086 10/1921 Carrier 131-135 1,551,676 9/1925 McConnell 131----136 X 1,976,487 10/1934 Elberty 68-9 2,322,272 6/1943 Bailey et al. 3446 X 2,679,115 5/1954 Bogaty et al 131136 X 2,768,629 10/1956 Maul 131--135 3,102,794 9/1963 Arnold 3446 X FOREIGN PATENTS 1,416,676 9/ 1965 France.

1,499 4/1881 Great Britain. 953,893 4/1964 Great Britain.

ALDRICH F. MEDBERY, Primary Examiner. 

13. A METHOD OF EXPELLING MOISTURE FROM TOBACCO, COMPRISING THE STEP OF CONVEYING MOIST TOBACCO THROUGH A CONDITIONING ZONE; CIRCULATING AT LEAST ONE CURRENT OF FRESH STREAM IN A CONFINING PATH EXTENDING INTO SAID ZONE WHEREBY SUCH STEAM EXPELS MOISTURE FROM TOBACCO AND ITS PRESSURE RESPECTIVELY RISES AND DROPS IN RESPONSE TO INDIRECT EXCHANGE OF HEAT WITH TOBACCO OF LOWER AND HIGHER MOISTURE CONTENT; CONVEYING THROUGH SAID ZONE A CURRENT OF HOT GAS IN DIRECT HEAT EXCHANGING RELATIONSHIP WITH TOBACCO TO EXPEL THEREFROM ADDITIONAL MOISTURE; MEASURING THE PRESSURE OF STEAM IN SAID CONFINING PATH; AND RESPECTIVELY RAISING AND REDUCING THE TEMPERATURE OF HOT GAS IN RESPONSE TO DECREASING AND INCREASING STEAM PRESSURE. 